Process for the preparation of 4,4'-stilbenedialdehydes

Abstract

The preparation of 4,4'-stilbenedialdehydes by reduction of 4,4'-stilbenedinitriles with an aluminium hydride.

What is claimed is: 
     
       1. A process for the preparation of a 4,4'-stilbenedialdehyde of formula ##STR6## wherein R 1  and R 2  are each independently of the other alkyl or alkoxy of 1 to 4 carbon atoms, phenyl, phenoxy, chlorine, bromine or C 1  -C 4  -dialkylamino, and m and n are each independently of the other 0, 1 or 2, which process comprises reacting a compound of formula ##STR7## wherein R 1 , R 2 , m and n have the given meanings, with an aluminum hydride, in an anhydrous, inert, aprotic organic solvent, thereafter subjecting the reaction mixture to acid hydrolysis, and isolating the compound of formula (1). 
     
     
       2. A process according to claim 1, wherein the solvent is a hydrocarbon, an ether or a mixture thereof. 
     
     
       3. A process according to claim 2, wherein the solvent is an alkane or cycloalkane, each of 5 to 10 carbon atoms, an aromatic hydrocarbon, dioxane, tetrahydrofuran, dibutyl ether, diethyl ether, or a mixture of said solvents. 
     
     
       4. A process according to claim 1, wherein the aluminium hydride is a compound of formula R 3  R 4  AlH, M[R 3  R 4  AlH 2  ] or MAlH 4 , wherein R 3  and R 4  are each independently of the other alkyl of 1 to 4 carbon atoms, and M is lithium or sodium. 
     
     
       5. A process according to claim 4, wherein the aluminium hydride is ( i  C 4  H 9 ) 2  AlH, Na[ i  (C 4  H 9 ) 2  AlH 2  ] or LiAlH 4 . 
     
     
       6. A process according to claim 1, wherein the acid hydrolysis is carried out in the presence of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid. 
     
     
       7. A process according to claim 1, wherein the reduction and the acid hydrolysis are carried out in the temperature range from 15° to 50° C. 
     
     
       8. A process according to claim 1, which comprises reacting the compound of formula (2), wherein m and n are 0, with ( i  C 4  H 9 ) 2  AlH at 15° to 25° C. in toluene, then subjecting the reaction mixture to hydrolysis in the presence of hydrochloric acid in the temperature range from 30° to 40° C., and isolating the compound of formula (1). 
     
     
       9. A process according to claim 8, wherein the molar ratio of the compound of formula (2) to aluminium hydride is 1:1 to 1:5.